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GATE 2026 Chemical Engineering Important Questions

GATE 2026 Important Questions in Chemical Engineering-CH Welcome to gatechemical.com - Your Gateway to Success!

Prepare for GATE 2026 with confidence using the expertly curated important questions in Chemical Engineering (CH), analyzed by the distinguished faculty of Engineers Institute of India (EII). Recognized as a benchmark for quality coaching and preparation exclusively for Chemical Engineering, EII is committed to helping you excel in the upcoming GATE examination.

DOWNLOAD GATE-2026 SAMPLE PAPER Practice Set-01

General Aptitude-Based on GATE Pattern
TYPE : MCQ ( Q.1 to Q.5 Carrying 1 Mark each)

Q.1 Which word completes the analogy "Fish is to Shoal as Lion is to _______"?

  • (A) Pride
  • (B) School
  • (C) Forest
  • (D) Series

Answer: (A)

Explanation:

Analogies are based on relationships between pairs of words, so we need to determine the specific relationship and apply it consistently.

Step 1: Analyze the Relationship

  • Fish and Shoal: A "shoal" is a collective noun for a group of fish that swim together loosely. It describes the social grouping of fish in their natural behavior.
  • The relationship is: Fish (individual animal) is part of a Shoal (the collective group of that animal).

Step 2: Apply the Relationship to Lion

  • Lion: We need the collective noun that represents a group of lions, similar to how a shoal represents a group of fish.
  • Lions are known to live and hunt in social groups. The standard collective noun for a group of lions is a pride.
  • Pride: A pride is the correct collective noun for a group of lions, directly analogous to a shoal for fish. Lions form prides, just as fish form shoals.

Q.2 Which sentence is grammatically correct?

  • (A) It is I who am responsible for this fiasco.
  • (B) It is myself who is responsible for this fiasco.
  • (C) It is I who is responsible for this fiasco.
  • (D) It is I who are responsible for this fiasco.

Answer: (A)

Explanation:

A - "It is I who am responsible" translates to "I am the one who am responsible," which is grammatically consistent:

I matches the subjective case.

am in "who am" agrees with I.

Other options fail:

  • B - misuses myself and has is (wrong person).

  • C - has is (wrong person for I).
  • D - has are (wrong number/person for I).
Thus, only option-A adheres to standard English grammar rules for pronoun case and subject-verb agreement.

Q.3 Cars P and Q start from point X in Gurugram at 10 AM. Car P heads North at 25 km/h and travels continuously, while Car Q heads East at 30 km/h but stops after 1 hour. If both are equidistant from X at 11:30 AM, how many minutes did Car Q stop for?

  • (A) 10
  • (B) 12
  • (C) 15
  • (D) 18

Answer: (C)

Explanation:

Step 1: Distance by car P at 11:30 AM

  • Time: 10:00 AM to 11:30 AM = 1.5 hours.
  • Speed: 25 km/h.
  • Distance: 25 × 1.5 = 37.5 km.

Step 2: Distance by car Q

  • Q travels 1 hour (10:00–11:00 AM) at 30 km/h = 30 km.
  • Q stops from 11:00 AM to 11:00 AM + t t t.
  • At 11:30 AM, Q’s distance must equal P’s = 37.5 km.

Step 3: Calculate Q’s travel time

  • To cover 37.5 km at 30 km/h:
  • Time: 37.5 ÷ 30 = 1.25 hours (1 hour 15 minutes).
  • Q travels until: 11:15 AM (10:00 AM + 1.25 hours).

Step 4: Find stoppage time

  • Q stops from: 11:15 AM to 11:30 AM.
  • Stoppage: 11:30 AM – 11:15 AM = 15 minutes.
So, Car Q stopped for 15 minutes.

Q.4 Which statement is NOT true for all real 𝑥 regarding floor and ceiling functions?

  • (A) ⌈𝑥⌉ ≥ 𝑥
  • (B) ⌊𝑥⌋ ≤ 𝑥
  • (C) ⌈𝑥⌉ ≥ ⌊𝑥⌋
  • (D) ⌊𝑥⌋ + 1 = ⌈𝑥⌉

Answer: (D)

Explanation:

The ceiling function ⌈x⌉ is the smallest integer ≥ x, and the floor function ⌊x⌋ is the largest integer ≤ x. We need to identify a statement that’s NOT true for all real x.

Common statement to test: ⌊x⌋ + 1 = ⌈x⌉

For x = 2.3:

  • ⌊2.3⌋ = 2, 2 + 1 = 3.
  • ⌈2.3⌉ = 3, true.

For x = 2:

  • ⌊2⌋ = 2, 2 + 1 = 3.
  • ⌈2⌉ = 2, false.
Since it fails when x is an integer, it’s NOT true for all x.

The statement ⌊x⌋ + 1 = ⌈x⌉ is NOT correct for all x.

Q.5 P and Q play chess. P wins 80%, draws 15%, and loses 5%. If they play 3 more matches, what is the probability that P wins exactly 2?

  • (A) 48/125
  • (B) 16/125
  • (C) 16/25
  • (D) 25/48

Answer: (A)

Explanation:

To find the probability that P wins exactly 2 of 3 chess matches against Q, given P's win rate is 80%, draw rate is 15%, and loss rate is 5%, we use the binomial probability formula. The outcomes are win, draw, or loss, but the question asks for the probability of exactly 2 wins, so we focus on wins versus non-wins.

Q.6 Select the most logical sentence sequence to form a paragraph.

P. At once, without thinking much, people rushed towards the city in hordes with the sole aim of grabbing as much gold as they could.

Q. However, little did they realize about the impending hardships they would have to face on their way to the city: miles of mud, unfriendly forests, hungry beasts and inimical local lords – all of which would reduce their chances of getting gold to almost zero.

R. All of them thought that easily they could lay their hands on gold and become wealthy overnight.

S. About a hundred years ago, the news that gold had been discovered in Kolar spread like wildfire and the whole State was in raptures.

  • (A) P → Q → R → S
  • (B) Q → S → R → P
  • (C) S → Q → P → R
  • (D) S → P → R → Q

Answer: (D)

Explanation:

Step 1: Analyze Sentence Connections

  • S sets the scene by introducing the gold discovery and public excitement, making it a natural starting point.
  • P describes the immediate reaction—people rushing to the city—logically following the news of gold.
  • R explains the mindset behind the rush (belief in easy wealth), which aligns with why people acted impulsively in P.
  • Q introduces the reality check—hardships that people didn't foresee—serving as a consequence or twist after the optimism in P and R.

Sequence and Flow

  • Sequence: Gold discovered, excitement spreads (S); people rush to the city (P); they believe they’ll get rich easily (R); but face unforeseen hardships (Q).
  • Flow: S introduces the event, P shows the action, R explains the motivation, and Q provides the consequence (hardships). Logical and cohesive.
The sequence S → P → R → Q creates a logical and cohesive flow in the narrative.

Q.7 If HIDE → 19-23-7-11 and CAGE → 5-2-17-11, what is the code for HIGH?

  • (A) 5-17-1-2
  • (B) 17-19-13-17
  • (C) 13-3-1-2
  • (D) 19-23-17-19

Answer: (D)

Explanation:

HIDE → 19-23-7-11

CAGE → 5-2-17-11

HIGH ⇒ 19-23-17-19

Q.8 A figure is reflected horizontally and then rotated 90° clockwise. Which is the resulting figure?

Answer: (B)

Explanation:

Anti-clockwise figure

Reflection along horizontal line figure

Q.9 Arrange in increasing order of lines of symmetry: Isosceles triangle, Equilateral triangle, Square, Circle.

  • (A) Circle; Square; Equilateral triangle; Isosceles triangle
  • (B) Isosceles triangle; Equilateral triangle; Square; Circle
  • (C) Equilateral triangle; Isosceles triangle; Square; Circle
  • (D) Isosceles triangle; Square; Equilateral triangle; Circle

Answer: (B)

Explanation:

The Correct Sequence of Objects Based on Increasing Number of Mirror Lines (Lines of Symmetry)

  • Isosceles Triangle: It has 1 line of symmetry.
  • Equilateral Triangle: It has 3 lines of symmetry.
  • Square: It has 4 lines of symmetry.
  • Circle: It has infinite lines of symmetry, as any line passing through the center is a line of symmetry.

Q.10 A student has 0.8 and 0.6 probability of job offers from Company S and T respectively. What is the probability of getting both?

  • (A) 0 ≤ p ≤ 0.2
  • (B) 0.4 ≤ p ≤ 0.6
  • (C) 0.2 ≤ p ≤ 0.4
  • (D) 0.6 ≤ p ≤ 1.0

Answer: (B)

Explanation: P (S) = 0.8 P (T) = 0.6 P (S∩T) = P (S) . P (T) = (0.8) . (0.6) = 0.48

Fundamentals & Theory | Important-Questions Set 01

1. What is the primary mode of heat transfer in a solid material with no bulk motion?
A) Convection
B) Radiation
C) Conduction
D) Evaporation
Answer: C
2. In steady-state heat conduction through a plane wall, the temperature distribution is:
A) Linear
B) Exponential
C) Parabolic
D) Random
Answer: A
3. The Fourier’s law of heat conduction is given by q = -k(dT/dx). What does 'k' represent?
A) Heat flux
B) Thermal conductivity
C) Temperature gradient
D) Heat transfer coefficient
Answer: B
4. In unsteady heat conduction, the temperature at a point varies with:
A) Time only
B) Space only
C) Both time and space
D) Neither time nor space
Answer: C
5. The Nusselt number (Nu) is a dimensionless parameter that represents the ratio of:
A) Convective to conductive heat transfer
B) Radiative to convective heat transfer
C) Conductive to radiative heat transfer
D) Total heat transfer to mass transfer
Answer: A
6. Which of the following is NOT a mode of heat transfer?
A) Conduction
B) Convection
C) Radiation
D) Sublimation
Answer: D
7. The thermal boundary layer thickness increases with:
A) Increasing Reynolds number
B) Decreasing Prandtl number
C) Increasing velocity of fluid
D) Decreasing thermal conductivity
Answer: B
8. In a double pipe heat exchanger, the overall heat transfer coefficient depends on:
A) Only the inner pipe material
B) Fouling factors and film coefficients
C) Only the outer pipe diameter
D) Fluid viscosity alone
Answer: B
9. The process of boiling involves:
A) Heat transfer from a solid to a liquid with phase change
B) Heat transfer without phase change
C) Only radiative heat transfer
D) Convection in gases
Answer: A
10. In a shell and tube heat exchanger, the baffles are used to:
A) Increase the pressure drop
B) Enhance the heat transfer by promoting turbulence
C) Reduce the flow rate
D) Insulate the tubes
Answer: B
11. The heat transfer coefficient in forced convection is primarily influenced by:
A) Fluid viscosity
B) Fluid velocity
C) Temperature gradient
D) All of the above
Answer: D
12. Which type of heat exchanger is most suitable for handling viscous fluids?
A) Plate heat exchanger
B) Shell and tube heat exchanger
C) Double pipe heat exchanger
D) Regenerative heat exchanger
Answer: C
13. In a multiple effect evaporator, the economy is improved by:
A) Using a single effect
B) Utilizing the vapor from one effect to heat the next
C) Increasing the feed temperature
D) Reducing the heat transfer area
Answer: B
14. The Stefan-Boltzmann law is related to:
A) Conduction heat transfer
B) Convective heat transfer
C) Radiative heat transfer
D) Boiling heat transfer
Answer: C
15. The LMTD (Log Mean Temperature Difference) correction factor is used in:
A) Single-pass heat exchangers
B) Multi-pass heat exchangers
C) Evaporators only
D) Radiation calculations
Answer: B
16. Condensation on a vertical surface is classified as:
A) Film-wise condensation
B) Drop-wise condensation
C) Nucleate boiling
D) Pool boiling
Answer: A
17. The design of a single effect evaporator requires consideration of:
A) Only the heat transfer coefficient
B) Feed rate, boiling point elevation, and heat transfer area
C) Fluid velocity alone
D) Radiation effects
Answer: B
18. The thermal resistance in a heat conduction process is inversely proportional to:
A) Area
B) Thickness
C) Thermal conductivity
D) Temperature difference
Answer: C
19. In a counter-flow heat exchanger, the temperature difference between the hot and cold fluids is:
A) Maximum at the inlet
B) Minimum at the outlet
C) Constant throughout
D) Maximum at the outlet
Answer: A
20. The overall heat transfer coefficient in a heat exchanger decreases due to:
A) Increased fluid velocity
B) Fouling on heat transfer surfaces
C) Higher thermal conductivity
D) Reduced temperature difference
Answer: B
21. The solution to the transient heat conduction in a semi-infinite solid subjected to a constant surface temperature is expressed using the error function. The Biot number in such a case must be:
A) Much greater than 1
B) Much less than 1
C) Equal to 1
D) Not relevant for semi-infinite solids
Answer: D
22. Why is the concept of thermal diffusivity more important in transient heat conduction than thermal conductivity?
A) Because it defines how quickly a material reaches thermal equilibrium
B) Because it determines the rate of heat generation
C) Because it affects the surface temperature only
D) Because it is only applicable to gases
Answer: A
23. In the context of radiative heat transfer, what is the physical meaning of a "black body"?
A) An object that reflects all incident radiation
B) An object that emits radiation only at a single wavelength
C) An ideal surface that absorbs and emits the maximum possible radiation
D) A real surface with zero emissivity
Answer: C
24. Why is the lumped capacitance method applicable only when the Biot number is very small?
A) Because the temperature within the object varies significantly
B) Because internal conduction resistance dominates
C) Because the entire body can be assumed at uniform temperature
D) Because it’s used only in boiling problems
Answer: C
25. Why does forced convection generally result in a higher heat transfer coefficient compared to natural convection?
A) Because it is only used in vacuum
B) Because fluid motion is driven by external means, enhancing mixing
C) Because natural convection doesn't transfer heat
D) Because it requires zero temperature difference
Answer: B

Exp : In forced convection, fans or pumps induce higher fluid velocities, leading to thinner thermal boundary layers and greater turbulence, which enhances convective heat transfer significantly.

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TYPE : MCQ Basic Level (Q.1–Q.15)

1. In molecular diffusion, the driving force is governed by:

A) Pressure gradient
B) Concentration gradient
C) Temperature gradient
D) Velocity gradient
Answer: B
Explanation: Molecular diffusion occurs due to a concentration gradient, as described by Fick’s first law (J = -D * dc/dx).

2. Fick’s second law applies to:

A) Steady-state diffusion
B) Unsteady-state diffusion
C) Convective mass transfer
D) Radiative mass transfer
Answer: B
Explanation: Fick’s second law (∂c/∂t = D * ∂²c/∂x²) describes the rate of change of concentration with time, applicable to unsteady-state diffusion.

3. The diffusion coefficient (D) in Fick’s law depends on:

A) Pressure only
B) Temperature and fluid properties
C) Velocity of fluid
D) Heat transfer rate
Answer: B
Explanation: The diffusion coefficient is influenced by temperature and the physical properties of the fluid, such as viscosity and molecular weight.

4. In a binary mixture, molecular diffusion is enhanced by:

A) Higher viscosity
B) Lower molecular weight difference
C) Higher temperature
D) Lower concentration gradient
Answer: C
Explanation: Higher temperatures increase molecular kinetic energy, enhancing diffusion rates in fluids.

5. The mass transfer coefficient (k) is defined as:

A) The rate of mass transfer per unit area
B) The ratio of mass flux to concentration difference
C) The inverse of diffusion coefficient
D) The thermal conductivity of the fluid
Answer: B
Explanation: The mass transfer coefficient relates the mass flux to the driving force (concentration difference) across a phase boundary.

6. Film theory assumes mass transfer occurs through:

A) A turbulent layer
B) A stagnant film layer
C) A convective layer
D) A renewable surface
Answer: B
Explanation: Film theory assumes a stagnant film at the interface where mass transfer occurs by molecular diffusion.

7. Penetration theory is based on:

A) Constant exposure time of the interface
B) Random renewal of the interface by eddies
C) Steady-state diffusion
D) A fixed film thickness
Answer: B
Explanation: Penetration theory posits that mass transfer occurs due to random renewal of the interface by turbulent eddies.

8. Surface renewal theory differs from film theory by:

A) Assuming a fixed film
B) Assuming continuous surface renewal
C) Ignoring diffusion
D) Applying only to gases
Answer: B
Explanation: Surface renewal theory assumes the interface is continuously renewed by fresh fluid, unlike the stagnant film in film theory.

9. The Chilton-Colburn analogy relates:

A) Heat and mass transfer only
B) Momentum, heat, and mass transfer
C) Conduction and convection
D) Diffusion and radiation
Answer: B
Explanation: The Chilton-Colburn analogy uses dimensionless numbers to relate momentum, heat, and mass transfer processes.

10. In stage-wise contacting, the efficiency is affected by:

A) Flow rate only
B) Contact time and equilibrium approach
C) Temperature gradient
D) Pressure drop
Answer: B
Explanation: Stage efficiency depends on the contact time between phases and how closely equilibrium is achieved.

11. Continuous contacting is characterized by:

A) Discrete equilibrium stages
B) Countercurrent or cocurrent flow of phases
C) Fixed mass transfer rates
D) Batch processing
Answer: B
Explanation: Continuous contacting involves a continuous flow of phases, typically countercurrent, for efficient mass transfer.

12. The stage efficiency in a distillation column is:

A) Always 100%
B) The ratio of actual to theoretical trays
C) Independent of reflux ratio
D) Constant for all conditions
Answer: B
Explanation: Stage efficiency is the ratio of the number of actual trays to the number of theoretical trays required.

13. HTU (Height of Transfer Unit) is used to:

A) Measure heat transfer efficiency
B) Determine the height for a unit concentration change
C) Calculate stage efficiency
D) Assess pressure drop
Answer: B
Explanation: HTU quantifies the height of packing required for a unit change in concentration in continuous contact equipment.

14. NTU (Number of Transfer Units) indicates:

A) The number of stages in batch process
B) The number of transfer units for a given separation
C) The heat transfer coefficient
D) The diffusion coefficient
Answer: B
Explanation: NTU represents the number of transfer units needed to achieve a specific degree of separation.

15. Distillation equipment design considers:

A) Only pressure differences
B) Reflux ratio and number of trays
C) Temperature only
D) Mass transfer coefficient alone
Answer: B
Explanation: Distillation design involves optimizing the reflux ratio and the number of trays for effective separation.

TYPE : MCQ Intermediate Level (Q.16-Q.30)

16. Absorption equipment operates on the principle of:

A) Gas-solid interaction
B) Gas-liquid mass transfer
C) Liquid-liquid extraction
D) Solid dissolution
Answer: B
Explanation: Absorption involves the transfer of a gas component into a liquid solvent, governed by mass transfer.

17. Leaching process efficiency depends on:

A) Gas flow rate
B) Solvent penetration and diffusion
C) Heat transfer rate
D) Pressure gradient
Answer: B
Explanation: Leaching efficiency relies on the solvent’s ability to penetrate the solid and the diffusion of solutes.

18. Liquid-liquid extraction requires:

A) Miscible liquids
B) Immiscible liquids with different solubilities
C) High pressure
D) No contact stages
Answer: B
Explanation: Liquid-liquid extraction separates components based on their solubility in two immiscible liquids.

19. Drying equipment design focuses on:

A) Condensation rate
B) Evaporation rate and airflow
C) Pressure drop
D) Liquid flow rate
Answer: B
Explanation: Drying design optimizes the evaporation rate of moisture, influenced by airflow and temperature.

20. Humidification is achieved by:

A) Removing moisture from air
B) Adding moisture to air
C) Increasing air temperature
D) Reducing pressure
Answer: B
Explanation: Humidification increases the moisture content of air, typically using water vapor or steam.

21. Dehumidification involves:

A) Adding heat to air
B) Removing moisture from air
C) Increasing humidity
D) Ignoring temperature
Answer: B
Explanation: Dehumidification reduces air moisture content, often by cooling or using desiccants.

22. Adsorption process depends on:

A) Bulk fluid mixing
B) Surface area and affinity
C) Liquid solubility
D) Pressure gradient
Answer: B
Explanation: Adsorption relies on the surface area of the adsorbent and the affinity of molecules to the surface.

23. Micro-filtration separates:

A) Dissolved salts
B) Particles larger than 0.1 micron
C) All ions
D) Gases only
Answer: B
Explanation: Micro-filtration removes particles and microorganisms larger than 0.1 micron using low pressure.

24. Ultra-filtration is effective for:

A) Desalination
B) Particles between 0.01 and 0.1 micron
C) Large solids
D) Gases
Answer: B
Explanation: Ultra-filtration filters particles and macromolecules in the range of 0.01 to 0.1 micron.

25. Nano-filtration targets:

A) All dissolved solids
B) Divalent and larger ions
C) Microorganisms only
D) Large particles
Answer: B
Explanation: Nano-filtration removes divalent and larger ions and organic molecules at moderate pressure.

26. Reverse osmosis is used for:

A) Removing large particles only
B) Water purification and salt removal
C) Low-pressure filtration
D) Gas separation
Answer: B
Explanation: Reverse osmosis purifies water by removing dissolved salts and impurities under high pressure.

27. The Sherwood number (Sh) relates to:

A) Heat transfer
B) Mass transfer
C) Momentum transfer
D) Both B and C
Answer: B
Explanation: The Sherwood number is a dimensionless parameter for convective mass transfer.

28. In a distillation column, equilibrium stage achievement depends on:

A) Constant flow
B) Contact time and mass transfer
C) Temperature only
D) Pressure drop
Answer: B
Explanation: Equilibrium stage achievement depends on contact time and the efficiency of mass transfer.

29. HTU decreases with:

A) Lower mass transfer rates
B) Higher mass transfer rates
C) Increased equipment height
D) Reduced flow rate
Answer: B
Explanation: HTU decreases with higher mass transfer rates, indicating better efficiency per unit height.

30. NTU increases with:

A) Lower separation efficiency
B) Higher separation efficiency
C) Constant flow rate
D) Reduced contact time
Answer: B
Explanation: NTU increases with higher separation efficiency, reflecting more transfer units needed.
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1. The first law of thermodynamics is based on the principle of:

  • A) Conservation of mass
  • B) Conservation of energy
  • C) Conservation of entropy
  • D) Conservation of momentum

Answer: B

Explanation: The first law states that the change in internal energy of a system is equal to the heat added minus the work done, embodying energy conservation.

2. For a closed system, the first law can be expressed as:

  • A) ΔU = Q - W
  • B) ΔH = Q + W
  • C) ΔS = Q/T
  • D) ΔG = ΔH - TΔS

Answer: A

Explanation: For a closed system, ΔU = Q - W, where ΔU is the change in internal energy, Q is heat added, and W is work done by the system.

3. In an open system, the first law includes:

  • A) Only heat and work
  • B) Mass flow terms
  • C) Entropy change
  • D) Gibbs free energy

Answer: B

Explanation: The first law for an open system includes mass flow terms (enthalpy of inlet and outlet streams) in addition to heat and work.

4. The second law of thermodynamics introduces the concept of:

  • A) Energy
  • B) Entropy
  • C) Pressure
  • D) Volume

Answer: B

Explanation: The second law states that the entropy of an isolated system always increases, introducing the concept of entropy as a measure of disorder.

5. A process with zero entropy change is:

  • A) Irreversible
  • B) Reversible
  • C) Adiabatic
  • D) Isothermal

Answer: B

Explanation: A reversible process occurs with no net entropy change, assuming ideal conditions with no irreversibilities.

6. The entropy change for an ideal gas undergoing isothermal expansion is given by:

  • A) ΔS = 0
  • B) ΔS = nR ln(V₂/V₁)
  • C) ΔS = nCv ln(T₂/T₁)
  • D) ΔS = nCp ln(P₂/P₁)

Answer: B

Explanation: For an ideal gas in isothermal expansion, ΔS = nR ln(V₂/V₁), where volume increases, leading to increased entropy.

7. The equation of state for an ideal gas is:

  • A) PV = nRT
  • B) P + a/V² = nRT
  • C) (P + a/V²)(V - b) = nRT
  • D) PVᵞ = constant

Answer: A

Explanation: The ideal gas law, PV = nRT, relates pressure, volume, and temperature for an ideal gas.

8. Residual properties are defined as:

  • A) Properties of pure substances
  • B) Difference between real and ideal gas properties
  • C) Properties at constant entropy
  • D) Properties of mixtures

Answer: B

Explanation: Residual properties account for the deviation of real gas behavior from ideal gas behavior using equations like the virial equation.

9. The partial molar property of a component in a mixture is:

  • A) The total property of the mixture
  • B) The property change with respect to the mole fraction of that component
  • C) The entropy of the mixture
  • D) The heat capacity of the component

Answer: B

Explanation: Partial molar property is the change in the extensive property of a mixture with the addition of one mole of the component, keeping other mole fractions constant.

10. Fugacity is a measure of:

  • A) Ideal gas behavior
  • B) Effective pressure accounting for non-ideality
  • C) Entropy change
  • D) Heat transfer

Answer: B

Explanation: Fugacity is an effective pressure that corrects for non-ideal behavior in real gases and mixtures.

11. Excess properties are related to:

  • A) Ideal mixture behavior
  • B) Deviation from ideal mixture behavior
  • C) Pure substance properties
  • D) Adiabatic processes

Answer: B

Explanation: Excess properties represent the deviation of a real mixture’s properties from those of an ideal mixture.

12. Activity coefficients are used to:

  • A) Calculate ideal gas properties
  • B) Account for non-ideal behavior in liquid mixtures
  • C) Determine entropy changes
  • D) Measure heat capacity

Answer: B

Explanation: Activity coefficients correct for non-ideal interactions in liquid mixtures, affecting phase equilibria.

13. Phase equilibrium for vapor-liquid systems is predicted using:

  • A) Gibbs phase rule
  • B) Raoult’s law
  • C) Newton’s law
  • D) Fourier’s law

Answer: B

Explanation: Raoult’s law predicts VLE by assuming the partial pressure of each component is proportional to its mole fraction in the liquid phase.

14. Chemical reaction equilibrium is governed by:

  • A) First law of thermodynamics
  • B) Second law of thermodynamics
  • C) Gibbs free energy minimization
  • D) Entropy maximization

Answer: C

Explanation: At equilibrium, a chemical reaction minimizes Gibbs free energy (ΔG = 0) under constant temperature and pressure.

15. For a closed system with no work done, the first law simplifies to:

  • A) ΔU = Q
  • B) ΔH = 0
  • C) ΔS = 0
  • D) ΔG = 0

Answer: A

Explanation: If no work is done (W = 0), the first law becomes ΔU = Q for a closed system, where ΔU is the change in internal energy and Q is the heat added to the system.

16. The entropy change for an irreversible process is:

  • A) Zero
  • B) Positive
  • C) Negative
  • D) Constant

Answer: B

Explanation: The second law of thermodynamics states that for an irreversible process, the entropy increases, indicating a positive change in entropy.

17. In an open system, the steady-state energy balance includes:

  • A) Only internal energy
  • B) Enthalpy flow and heat transfer
  • C) Entropy flow
  • D) Work done by friction

Answer: B

Explanation: In a steady-state energy balance, both enthalpy flow due to mass transfer and heat transfer are considered, with accumulation typically neglected.

18. The Clausius inequality relates to:

  • A) Energy conservation
  • B) Entropy increase in irreversible cycles
  • C) Heat transfer coefficient
  • D) Mass transfer rate

Answer: B

Explanation: The Clausius inequality (∫δQ/T ≤ 0) describes the entropy change for irreversible processes, indicating entropy increase in irreversible cycles.

19. The compressibility factor (Z) for a real gas is:

  • A) Always 1
  • B) PV/nRT
  • C) Depends on pressure and temperature
  • D) Zero for ideal gases

Answer: C

Explanation: The compressibility factor Z = PV/nRT quantifies the deviation of a real gas from ideal gas behavior. It depends on both pressure and temperature.

20. Partial molar enthalpy of a mixture component is:

  • A) The total enthalpy
  • B) The enthalpy change with mole fraction
  • C) The heat of reaction
  • D) The entropy change

Answer: B

Explanation: Partial molar enthalpy is the change in the enthalpy of a mixture due to the addition of one mole of a component, keeping the mole fractions of other components constant.

21. The fugacity coefficient approaches 1 for:

  • A) High pressures
  • B) Ideal gases
  • C) Low temperatures
  • D) Real liquids

Answer: B

Explanation: Fugacity coefficient equals 1 for ideal gases where non-ideal effects are negligible.

22. Excess Gibbs free energy is zero for:

  • A) Real mixtures
  • B) Ideal mixtures
  • C) Non-ideal gases
  • D) Pure substances

Answer: B

Explanation: Excess Gibbs free energy is zero for ideal mixtures where intermolecular interactions are absent.

23. VLE prediction using activity coefficients requires:

  • A) Ideal gas law
  • B) Non-ideal solution models
  • C) Constant pressure
  • D) No temperature effect

Answer: B

Explanation: Activity coefficients account for non-ideal behavior in liquid phases for accurate VLE prediction.

24. Chemical equilibrium constant (K) is related to:

  • A) Entropy change
  • B) Gibbs free energy change
  • C) Enthalpy change
  • D) Internal energy

Answer: B

Explanation: K = exp(-ΔG°/RT), where ΔG° is the standard Gibbs free energy change.

25. For a reversible adiabatic process, entropy change is:

  • A) Positive
  • B) Negative
  • C) Zero
  • D) Infinite

Answer: C

Explanation: In a reversible adiabatic process (Q = 0), entropy change is zero due to no heat transfer.

26. The first law application to a turbine involves:

  • A) Only work output
  • B) Enthalpy drop and work
  • C) Entropy increase
  • D) Heat input

Answer: B

Explanation: The first law for a turbine relates the enthalpy drop across the turbine to the work output.

27. The second law efficiency is defined as:

  • A) Work output/Heat input
  • B) Actual entropy change/Ideal entropy change
  • C) Reversible work/Actual work
  • D) Heat transfer rate

Answer: C

Explanation: Second law efficiency is the ratio of reversible work to actual work, indicating process perfection.

28. Residual enthalpy depends on:

  • A) Ideal gas properties
  • B) Real gas deviations
  • C) Constant volume
  • D) Temperature only

Answer: B

Explanation: Residual enthalpy accounts for deviations of real gas behavior from ideal gas properties.

29. The activity coefficient of an ideal solution is:

  • A) Zero
  • B) One
  • C) Infinite
  • D) Negative

Answer: B

Explanation: In an ideal solution, activity coefficients are 1 due to no deviation from Raoult’s law.

30. In GATE 2023, a question on entropy change for an ideal gas matched with:

  • A) Isothermal process
  • B) Adiabatic process
  • C) Polytropic process
  • D) Isobaric process

Answer: A

Explanation: GATE 2023 included a problem on entropy change (ΔS = nR ln(V₂/V₁)) for an ideal gas in isothermal expansion.

31. In GATE 2022, a problem on first law for an open system involved:

  • A) Only heat transfer
  • B) Enthalpy balance with mass flow
  • C) Entropy balance
  • D) Work only

Answer: B

Explanation: GATE 2022 featured an open system energy balance with enthalpy flow terms, matching practical applications.

32. GATE 2021 tested the second law with:

  • A) Entropy increase in a cycle
  • B) Energy conservation
  • C) Heat transfer coefficient
  • D) Mass transfer rate

Answer: A

Explanation: A GATE 2021 question involved entropy increase in an irreversible cycle, aligning with second law principles.

33. A GATE 2023 question on equation of state involved:

  • A) Ideal gas law
  • B) Van der Waals equation
  • C) Bernoulli equation
  • D) Continuity equation

Answer: B

Explanation: GATE 2023 included a problem using the Van der Waals equation for real gas behavior.

34. GATE 2024 tested partial molar properties in:

  • A) Pure substances
  • B) Binary mixtures
  • C) Ternary systems
  • D) Ideal gases

Answer: B

Explanation: A GATE 2024 question calculated partial molar volume in a binary mixture.

35. Fugacity was a focus in GATE 2025 with:

  • A) Ideal gas
  • B) Real gas at high pressure
  • C) Liquid mixtures
  • D) Constant entropy

Answer: B

Explanation: GATE 2025 featured a fugacity calculation for a real gas under high pressure conditions.

36. GATE 2022 included VLE prediction using:

  • A) Dalton’s law
  • B) Raoult’s law
  • C) Henry’s law
  • D) Gibbs-Duhem equation

Answer: B

Explanation: A GATE 2022 problem used Raoult’s law to predict VLE for an ideal system.

37. Chemical equilibrium in GATE 2023 involved:

  • A) Enthalpy balance
  • B) Gibbs free energy minimization
  • C) Entropy maximization
  • D) Heat transfer

Answer: B

Explanation: GATE 2023 tested chemical equilibrium using Gibbs free energy minimization.

38. GATE 2024 questioned entropy change for:

  • A) Isothermal expansion
  • B) Adiabatic compression
  • C) Isobaric cooling
  • D) Isochoric heating

Answer: A

Explanation: A GATE 2024 problem calculated entropy change for an ideal gas in isothermal expansion.

39. GATE 2021 tested residual properties for:

  • A) Ideal mixtures
  • B) Real gases
  • C) Pure liquids
  • D) Solid phases

Answer: B

Explanation: GATE 2021 included a residual enthalpy calculation for a real gas.

40. Activity coefficients appeared in GATE 2025 for:

  • A) Ideal solutions
  • B) Non-ideal liquid mixtures
  • C) Gas phases
  • D) Solid solutions

Answer: B

Explanation: GATE 2025 featured activity coefficients to account for non-ideal behavior in liquid mixtures.

  • GATE 2026 Thermodynamics-Thermo: Basics Fundamentals Practice 01
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  • GATE 2026 Thermodynamics-Thermo: Numerical Based Practice 01
  • GATE 2026 Thermodynamics-Thermo: Numerical Based Practice 02
  • GATE 2026 Thermodynamics-Thermo: Numerical Based Practice 03

Basic Level (1–10)

1. What is the pressure at a depth of 10 m in water (density 1000 kg/m³)?
A) 98.1 kPa
B) 49.05 kPa
C) 196.2 kPa
D) 9.81 kPa
Answer: A
Explanation: P = ρgh = 1000 × 9.81 × 10 = 98100 Pa = 98.1 kPa.
2. Surface tension is caused by:
A) Cohesive forces
B) Adhesive forces
C) Gravitational forces
D) Frictional forces
Answer: A
Explanation: Surface tension arises from cohesive forces between molecules at the liquid surface.
3. Which fluid obeys Newton’s law of viscosity?
A) Blood
B) Paint
C) Water
D) Ketchup
Answer: C
Explanation: Water is a Newtonian fluid where shear stress is proportional to shear rate.
4. The viscosity of a gas typically:
A) Decreases with temperature
B) Increases with temperature
C) Remains constant
D) Decreases with pressure
Answer: B
Explanation: Gas viscosity increases with temperature due to increased molecular collisions.
5. The Bernoulli equation assumes:
A) Viscous flow
B) Incompressible flow
C) Turbulent flow
D) Unsteady flow
Answer: B
Explanation: Bernoulli’s equation applies to inviscid, incompressible, steady flow along a streamline.
6. The equation of continuity is based on:
A) Conservation of energy
B) Conservation of mass
C) Conservation of momentum
D) Conservation of force
Answer: B
Explanation: Continuity ensures mass flow rate is constant in a control volume.
7. What does the friction factor depend on in laminar flow?
A) Reynolds number
B) Pipe length
C) Fluid density
D) Pipe roughness
Answer: A
Explanation: In laminar flow, f = 16/Re, independent of roughness.
8. Dimensional analysis is used to:
A) Increase flow rate
B) Reduce variables
C) Measure viscosity
D) Calculate pressure
Answer: B
Explanation: It simplifies problems by forming dimensionless groups.
9. The velocity profile in laminar pipe flow is:
A) Flat
B) Parabolic
C) Linear
D) Exponential
Answer: B
Explanation: Hagen-Poiseuille flow yields a parabolic velocity profile.
10. Venturi meters measure flow based on:
A) Pressure difference
B) Temperature change
C) Viscosity
D) Density
Answer: A
Explanation: Venturi meters use Bernoulli’s principle to relate pressure drop to flow rate.

Intermediate Level (11–25)

11. What is the pressure difference (in Pa) due to surface tension in a 1 mm diameter water droplet (σ = 0.073 N/m)?

  • A) 146
  • B) 73
  • C) 292
  • D) 36.5

Answer: A

Explanation: ΔP = 4σ/d = 4 × 0.073 / 0.001 = 146 Pa.

12. A non-Newtonian fluid exhibits:

  • A) Constant viscosity
  • B) Shear-thinning behavior
  • C) Linear stress-strain
  • D) Zero viscosity

Answer: B

Explanation: Non-Newtonian fluids like pseudoplastics show viscosity decreasing with shear rate.

13. The Navier-Stokes equation represents:

  • A) Energy balance
  • B) Momentum balance
  • C) Mass balance
  • D) Friction factor

Answer: B

Explanation: It’s the differential form of momentum conservation.

14. In turbulent flow, friction factor depends on:

  • A) Reynolds number only
  • B) Pipe roughness and Re
  • C) Fluid viscosity only
  • D) Pipe length

Answer: B

Explanation: Turbulent f is a function of Re and relative roughness (Moody chart).

15. The Buckingham Pi theorem determines:

  • A) Flow velocity
  • B) Number of dimensionless groups
  • C) Pressure drop
  • D) Pipe diameter

Answer: B

Explanation: It calculates π terms as variables minus dimensions.

16. For laminar flow in a pipe, pressure drop is proportional to:

  • A) Velocity squared
  • B) Velocity
  • C) Pipe diameter
  • D) Fluid density

Answer: B

Explanation: ΔP = (32μLv)/D² from Hagen-Poiseuille.

17. Orifice meters are less accurate than Venturi meters due to:

  • A) Higher energy loss
  • B) Lower cost
  • C) Smaller size
  • D) Simpler design

Answer: A

Explanation: Orifice plates cause more permanent pressure loss.

18. The boundary layer thickness increases with:

  • A) Decreasing velocity
  • B) Increasing distance
  • C) Decreasing viscosity
  • D) Increasing density

Answer: B

Explanation: δ ∝ √x in laminar boundary layers.

19. Drag force on a sphere in Stokes’ regime is proportional to:

  • A) Velocity squared
  • B) Velocity
  • C) Diameter squared
  • D) Density

Answer: B

Explanation: Fd = 6πμrv (Stokes’ law).

20. In a packed bed, pressure drop follows:

  • A) Darcy’s law
  • B) Ergun equation
  • C) Bernoulli equation
  • D) Hagen-Poiseuille

Answer: B

Explanation: Ergun accounts for both viscous and inertial losses.

21. The power law index (n) for a shear-thinning fluid is:

  • A) n > 1
  • B) n = 1
  • C) n < 1
  • D) n = 0

Answer: C

Explanation: Shear-thinning fluids have n < 1 in τ = K(γ̇)n.

22. The mechanical energy equation includes losses due to:

  • A) Friction
  • B) Elevation
  • C) Velocity
  • D) All of the above

Answer: D

Explanation: It balances kinetic, potential, and frictional losses.

23. In turbulent flow, the universal velocity profile shows:

  • A) Linear region near wall
  • B) Logarithmic region
  • C) Parabolic shape
  • D) Constant velocity

Answer: B

Explanation: The log-law region dominates in turbulent flow.

24. Minimum fluidization velocity depends on:

  • A) Particle size and density
  • B) Fluid viscosity only
  • C) Pipe diameter
  • D) Flow rate

Answer: A

Explanation: Vmf is derived from force balance (Ergun equation).

25. Pressure drop in turbulent flow is proportional to:

  • A) Velocity
  • B) Velocity squared
  • C) Pipe length squared
  • D) Fluid viscosity

Answer: B

Explanation: ΔP ∝ v² in turbulent flow (Darcy-Weisbach).

TYPE : MCQ Basic Level (Q.1–Q15)

1. What is the primary factor determining particle shape?

A) Size
B) Material properties
C) Temperature
D) Pressure
Answer: B
Explanation: Particle shape depends on the inherent properties of the material, such as crystallinity or amorphous nature, rather than external factors like size or temperature.

2. Which instrument is commonly used to measure particle size distribution?

A) Sieve shaker
B) Thermometer
C) Barometer
D) Hydrometer
Answer: A
Explanation: Sieve shakers are widely used to determine particle size distribution by separating particles into size fractions.

3. What is the purpose of size reduction in mechanical operations?

A) Increase particle size
B) Improve handling
C) Reduce energy consumption
D) Prevent mixing
Answer: B
Explanation: Size reduction enhances material handling, reactivity, and downstream processing efficiency.

4. Which law governs energy required for size reduction?

A) Newton’s Law
B) Rittinger’s Law
C) Boyle’s Law
D) Charles’ Law
Answer: B
Explanation: Rittinger’s Law states that energy required for size reduction is proportional to the new surface area created.

5. What is free settling?

A) Settling under gravity without interference
B) Settling with particle collisions
C) Settling in a centrifuge
D) Settling with agitation
Answer: A
Explanation: Free settling occurs when particles settle individually under gravity without interaction.

6. What is the main force in a centrifuge?

A) Gravitational force
B) Centrifugal force
C) Magnetic force
D) Frictional force
Answer: B
Explanation: Centrifuges use centrifugal force to separate particles based on density differences.

7. Cyclones primarily separate particles based on:

A) Size
B) Shape
C) Density
D) Temperature
Answer: A
Explanation: Cyclones use centrifugal action to separate particles primarily by size.

8. What is the purpose of thickening?

A) Reduce solid concentration
B) Increase liquid volume
C) Concentrate solids
D) Filter gases
Answer: C
Explanation: Thickening increases the solid content in a slurry by settling.

9. Filtration separates:

A) Solids from liquids
B) Liquids from gases
C) Solids from gases
D) Gases from liquids
Answer: A
Explanation: Filtration uses a medium to separate suspended solids from a liquid.

10. What drives agitation in mixing?

A) Gravity
B) Mechanical energy
C) Heat
D) Pressure
Answer: B
Explanation: Agitation relies on mechanical energy from impellers or stirrers.

11. Which equipment is used for conveying solids?

A) Belt conveyor
B) Pump
C) Valve
D) Fan
Answer: A
Explanation: Belt conveyors are standard for transporting solid materials.

12. Particle size is typically measured in:

A) Meters
B) Microns
C) Liters
D) Kilograms
Answer: B
Explanation: Microns (µm) are commonly used to measure small particle sizes.

13. What is hindered settling?

A) Settling without interference
B) Settling with particle interactions
C) Settling in a vacuum
D) Settling with filtration
Answer: B
Explanation: Hindered settling occurs when particle concentration affects settling velocity.

14. The efficiency of a cyclone depends on:

A) Inlet velocity
B) Temperature
C) Pressure
D) Humidity
Answer: A
Explanation: Higher inlet velocity improves cyclone separation efficiency.

15. What is the primary goal of classification?

A) Mix particles
B) Separate particles by size
C) Reduce particle size
D) Increase density
Answer: B
Explanation: Classification separates particles into size fractions.

TYPE : Intermediate Level (Q.16–Q.25)

16. Which method is best for fine particle size analysis?

A) Sieving
B) Sedimentation
C) Crushing
D) Mixing
Answer: B
Explanation: Sedimentation is effective for analyzing fine particles based on settling rates.

17. Kick’s Law applies to:

A) Fine grinding
B) Coarse crushing
C) Filtration
D) Mixing
Answer: B
Explanation: Kick’s Law states energy is proportional to the size reduction ratio, suitable for coarse crushing.

18. Stokes’ Law is used to calculate:

A) Settling velocity
B) Filtration rate
C) Mixing speed
D) Conveyor speed
Answer: A
Explanation: Stokes’ Law predicts the settling velocity of spherical particles in a fluid.

19. What enhances centrifuge separation?

A) Lower speed
B) Higher rotational speed
C) Increased temperature
D) Reduced pressure
Answer: B
Explanation: Higher speed increases centrifugal force, improving separation.

20. In thickening, underflow refers to:

A) Clear liquid
B) Concentrated slurry
C) Gas output
D) Filtered solids
Answer: B
Explanation: Underflow is the thickened solid-liquid mixture exiting the thickener.

21. Cake filtration occurs when:

A) Solids form a layer on the filter
B) Liquid passes through freely
C) Gas is filtered
D) Mixing occurs
Answer: A
Explanation: Cake filtration involves solids building up on the filter medium.

22. Which impeller is best for high-viscosity mixing?

A) Propeller
B) Turbine
C) Anchor
D) Paddle
Answer: C
Explanation: Anchor impellers are designed for high-viscosity fluids.

23. Pneumatic conveying uses:

A) Water
B) Air
C) Gravity
D) Mechanical belts
Answer: B
Explanation: Pneumatic conveying transports solids using air pressure or vacuum.

24. Screen effectiveness depends on:

A) Mesh size
B) Temperature
C) Pressure
D) Color
Answer: A
Explanation: Mesh size determines the particle sizes separated by a screen.

25. What reduces settling velocity in hindered settling?

A) Low particle concentration
B) High particle concentration
C) High temperature
D) Low viscosity
Answer: B
Explanation: High concentration causes particle interactions, slowing settling.
  • GATE 2026 Mechanical Operations-MO: Basics Fundamentals Practice 01
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TYPE : GATE-Matched MCQ Questions (Q.1–Q.10)

1. In a steady-state process, the accumulation term in a mass balance equation is:

A) Zero
B) Unity
C) Time-dependent
D) Equal to the inlet flow rate
Answer: A
Explanation: In steady-state conditions, there is no accumulation of mass in the system.

2. A system with two phases and two components is in equilibrium. According to Gibbs’ phase rule, the degrees of freedom are:

A) 0
B) 2
C) 1
D) 3
Answer: B
Explanation: Gibbs' phase rule for a two-phase, two-component system gives 2 degrees of freedom.

3. The main purpose of a tie component in mass balance calculations is to:

A) React with other components
B) Represent inert species
C) Indicate phase change
D) Reduce number of unknowns
Answer: B
Explanation: A tie component is an inert species used to simplify mass balance calculations by reducing unknowns.

4. In a process, 100 kg/h of feed is split into 60 kg/h recycle and 40 kg/h product. What is the recycle ratio?

A) 0.4
B) 1.5
C) 1.0
D) 0.6
Answer: B
Explanation: Recycle ratio = Recycle Flow / Product Flow = 60 / 40 = 1.5.

5. Which of the following statements is true about an unsteady-state system?

A) Input = Output
B) Accumulation = 0
C) Properties vary with time
D) It is always at equilibrium
Answer: C
Explanation: In unsteady-state systems, properties change with time due to transient conditions.

6. In a non-reacting distillation process with a bypass stream, the overall mass balance must include:

A) Only the feed stream
B) Feed and bypass streams
C) Only product streams
D) Only tie components
Answer: B
Explanation: The mass balance must include all streams that enter and leave the system, including the bypass.

7. Which term accounts for the mass that is not part of the main process stream and returns for further processing?

A) Bypass
B) Product
C) Recycle
D) Purge
Answer: C
Explanation: Recycle refers to the mass that is returned to the process for further processing.

8. In a multiphase system with 3 components and 2 phases, how many degrees of freedom are there (at equilibrium)?

A) 4
B) 2
C) 3
D) 5
Answer: C
Explanation: Using Gibbs' phase rule, degrees of freedom = C - P + 2 = 3 - 2 + 2 = 3.

9. Which process balance is more suitable for analyzing combustion reactions?

A) Mass balance only
B) Energy balance only
C) Both mass and energy balance
D) Phase equilibrium
Answer: C
Explanation: Both mass and energy balances are necessary to analyze combustion reactions, as they involve both material and energy transformations.

10. In a chemical process, if a purge stream is removed, what could potentially accumulate in the system?

A) Reactants
B) Desired products
C) Inert or undesired components
D) Solvents
Answer: C
Explanation: If a purge stream is removed, inert or undesired components might accumulate in the system.

TYPE : Basics Theoretical MCQ Questions (Q.11–Q.25)

11. Which of the following is NOT a component of a general mass balance equation?

A) Input
B) Output
C) Accumulation
D) Viscosity
Answer: D
Explanation: Viscosity is not part of the basic mass balance equation, which includes input, output, and accumulation.

12. What is the degree of freedom for a single-phase binary mixture at constant temperature and pressure?

A) 0
B) 1
C) 2
D) 3
Answer: B
Explanation: The degree of freedom for a binary mixture at constant temperature and pressure is 1.

13. A process stream contains a non-volatile solute and water. Which is the tie component during evaporation?

A) Water
B) Air
C) Solute
D) Vapor
Answer: C
Explanation: In evaporation, the solute acts as the tie component because it doesn't evaporate, while water does.

14. Which of the following represents a closed system?

A) Continuous distillation column
B) Batch reactor with no inflow or outflow
C) Flash evaporator
D) CSTR with input and output streams
Answer: B
Explanation: A batch reactor with no inflow or outflow is a closed system, meaning no mass enters or leaves.

15. The use of bypass stream is advantageous when:

A) Reaction conversion is complete
B) Certain property of product must match feed
C) No energy is required
D) Total flow rate needs to be minimized
Answer: B
Explanation: A bypass stream is used when the product must match a certain property of the feed, such as composition.

16. The presence of an inert component in a chemical reaction system:

A) Affects the stoichiometry
B) Alters the equilibrium constant
C) Does not participate in reaction
D) Is always undesirable
Answer: C
Explanation: Inert components do not participate in the reaction, but they can influence the system's mass balance.

17. The steady-state energy balance does not include which of the following?

A) Heat input
B) Work done
C) Change in internal energy
D) Time-dependent term
Answer: D
Explanation: In a steady-state system, there is no time-dependent term because the system is not changing with time.

18. In which case would a purge stream be absolutely necessary?

A) When feed is pure
B) In the presence of a non-reacting inert gas
C) In a continuous reactor with full conversion
D) For batch operations
Answer: B
Explanation: A purge stream is necessary in systems with non-reacting inert gases to prevent accumulation of inert material.

19. Gibb’s phase rule can be applied to:

A) Only single-phase systems
B) Any system at equilibrium
C) Open systems only
D) Systems with only ideal gases
Answer: B
Explanation: Gibb's phase rule is applicable to any system at equilibrium, whether single-phase or multi-phase.

20. The main purpose of mass transfer operations is:

A) To ensure energy conservation
B) To achieve separation of components
C) To decrease the concentration of a solute
D) To increase product yield
Answer: B
Explanation: Mass transfer operations are primarily used for separating components in a mixture.

21. The principle behind a distillation column is based on:

A) Mass transfer
B) Chemical reaction
C) Fluid dynamics
D) Heat exchange
Answer: A
Explanation: Distillation works based on mass transfer, where components of a mixture are separated due to their different volatilities.

22. Which of the following represents the correct order of stages in a distillation process?

A) Condensation, Vaporization
B) Vaporization, Condensation
C) Evaporation, Precipitation
D) Adsorption, Desorption
Answer: B
Explanation: In distillation, the mixture is vaporized first, then condensed to separate the components.

23. The velocity at which a particle settles in a liquid depends on:

A) The diameter of the particle
B) The density of the liquid
C) The temperature of the liquid
D) All of the above
Answer: D
Explanation: The settling velocity of a particle depends on several factors, including the particle's diameter, the density of the liquid, and the liquid's temperature.

24. The main disadvantage of using a batch reactor as compared to a continuous reactor is:

A) Higher throughput
B) Continuous monitoring of reaction
C) Inefficient use of equipment
D) Higher energy consumption
Answer: C
Explanation: Batch reactors typically have lower throughput and are less efficient in equipment usage compared to continuous reactors.

25. Which of the following best describes an isothermal process?

A) Temperature remains constant while pressure changes
B) Temperature remains constant while volume changes
C) Pressure remains constant while volume changes
D) Both temperature and pressure change
Answer: B
Explanation: In an isothermal process, the temperature remains constant while the volume or pressure can change.
  • GATE 2026 Process Calculations-PC: Basics Fundamentals Practice 01
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  • GATE 2026 Process Calculations-PC: Numerical Based Practice 01
  • GATE 2026 Process Calculations-PC: Numerical Based Practice 02
  • GATE 2026 Process Calculations-PC: Numerical Based Practice 03

1. The rate of a chemical reaction is defined as:

A) Change in concentration of products per unit time
B) Change in concentration of reactants per unit time
C) Either A or B
D) Constant over time
Answer: C
Explanation: Reaction rate is expressed as the change in concentration of either reactants or products over time.

2. For the reaction sequence A→B→C, maximum yield of B is obtained by:

A) Using a PFR
B) Using a CSTR
C) Operating at high conversion
D) Operating at low temperature
Answer: B
Explanation: For intermediate product formation in series reactions, CSTR allows better control by minimizing further conversion of B to C.

3. Which of the following reactors assumes perfect mixing?

A) Plug Flow Reactor
B) Packed Bed Reactor
C) Continuous Stirred Tank Reactor (CSTR)
D) Tubular Reactor
Answer: C

4. Which of the following is NOT a characteristic of an elementary reaction?

A) Reaction order equals molecularity
B) Follows simple rate law
C) Involves a complex mechanism
D) No intermediates are formed
Answer: C
Explanation: Elementary reactions do not involve complex mechanisms or intermediates; their rate law directly follows stoichiometry.

5. The half-life of a first-order reaction is:

A) Dependent on the initial concentration
B) Independent of the initial concentration
C) Dependent on pressure
D) Dependent on temperature only
Answer: B

6. Enzyme kinetics follow Michaelis-Menten behavior when:

A) Enzyme concentration is high
B) Substrate concentration is high
C) Product formation is neglected
D) Enzyme inhibition is considered
Answer: B

7. In a PFR with constant density and steady-state conditions, the conversion increases:

A) Linearly with length
B) Exponentially with length
C) As a function of residence time
D) Cannot be predicted
Answer: C

8. In Michaelis-Menten enzyme kinetics, at very high substrate concentration, the reaction rate becomes:

A) First-order with respect to substrate
B) Zero-order with respect to substrate
C) Second-order with respect to enzyme
D) Inversely proportional to substrate
Answer: B
Explanation: At high substrate concentration, enzyme sites are saturated and rate becomes independent of substrate concentration (zero-order).

9. A second-order reaction A → products follows the rate law:

A) r = k[A]
B) r = k[A]²
C) r = k[A][B]
D) r = k
Answer: B

10. (GATE 2022) For a first-order irreversible reaction in a PFR, the relation between conversion (X) and reactor volume (V) is:

A) Linear
B) Logarithmic
C) Exponential
D) Polynomial
Answer: B

11. (GATE 2021) In the context of catalyst deactivation, which statement is true?

A) Activity increases with time
B) Activity is constant
C) Activity decreases due to sintering or poisoning
D) Deactivation is reversible always
Answer: C

12. (GATE 2020) The residence time distribution (RTD) function E(t) for an ideal CSTR is:

A) Delta function
B) Uniform distribution
C) Exponential decay
D) Step function
Answer: C

13. Non-isothermal reactors need energy balance due to:

A) Temperature-independent reactions
B) Reactions with negligible heat effect
C) Reactions with significant heat generation/absorption
D) Ideal mixing
Answer: C

14. The selectivity in a multiple reaction system is defined as:

A) Conversion of A
B) Ratio of desired product to total products
C) Reaction rate of B
D) Enthalpy change
Answer: B

15. In heterogeneous catalysis, the rate-determining step can be:

A) Bulk diffusion
B) Adsorption
C) Surface reaction
D) Any of the above
Answer: D

16. The Thiele modulus is used in:

A) Homogeneous reaction modeling
B) RTD analysis
C) Assessing internal diffusion effects in porous catalysts
D) Isothermal reactor design
Answer: C

17. The conversion in an adiabatic reactor is limited by:

A) Initial concentration
B) Inlet pressure
C) Heat of reaction
D) Catalyst deactivation
Answer: C

18. The effectiveness factor (η) is defined as:

A) Ratio of actual to maximum possible rate
B) Ratio of surface to bulk concentration
C) Conversion to initial concentration
D) None of the above
Answer: A

19. The Monod model is used to describe:

A) Catalytic cracking
B) Bioreactor kinetics
C) Homogeneous catalysis
D) Batch reactor design
Answer: B

20. In an isothermal PFR, conversion increases with:

A) Decreasing pressure
B) Increasing reactor length
C) Decreasing catalyst activity
D) None of these
Answer: B

GATE Pattern Questions (2020–2025)

21. (GATE 2023) For a zero-order reaction, the rate of reaction is:

A) Constant
B) Proportional to concentration
C) Inversely proportional to temperature
D) Dependent on pressure
Answer: A

22. (GATE 2024) The integral method of analyzing kinetic data is useful for:

A) Reversible reactions
B) Gas-phase reactions only
C) Simple rate laws
D) Complex mechanisms
Answer: C

23. (GATE 2021) The RTD curve for ideal plug flow is:

A) Exponential
B) Step function
C) Dirac delta function
D) Linear
Answer: C

24. (GATE 2022) Conversion in a batch reactor is found by integrating:

A) dC/dt = -kC
B) dX/dt = r
C) dX/dt = -k
D) dX/dt = 1
Answer: B

25. (GATE 2020) Catalyst deactivation due to coking is:

A) Physical
B) Chemical
C) Biological
D) Irreversible
Answer: D

Frequently Asked Questions-PSUs

26. A catalyst increases the rate of reaction by:

A) Changing equilibrium
B) Increasing temperature
C) Decreasing activation energy
D) Increasing product formation
Answer: C

27. An ideal batch reactor is best suited for:

A) Large scale continuous production
B) High-volume gases
C) Small-scale reactions and kinetic studies
D) Steady-state operations
Answer: C

28. Which model is used for non-ideal reactors?

A) CSTR
B) PFR
C) Dispersion model
D) Batch model
Answer: C

29. Catalyst surface area plays a crucial role in:

A) Adsorption equilibrium
B) Reaction mechanism
C) Rate of heterogeneous catalysis
D) All of the above
Answer: D

30. For an elementary reaction, the order of the reaction is:

A) Equal to the molecularity
B) Always zero
C) Always one
D) Independent of molecularity
Answer: A
Explanation: For elementary reactions, the reaction order equals the number of reacting molecules (molecularity).
  • GATE 2026 Chemical Reaction Engineering-CRE: Basics Fundamentals Practice 01
  • GATE 2026 Chemical Reaction Engineering-CRE: Basics Fundamentals Practice 02
  • GATE 2026 Chemical Reaction Engineering-CRE: Basics Fundamentals Practice 03
  • GATE 2026 Chemical Reaction Engineering-CRE: Numerical Based Practice 01
  • GATE 2026 Chemical Reaction Engineering-CRE: Numerical Based Practice 02
  • GATE 2026 Chemical Reaction Engineering-CRE: Numerical Based Practice 03

TYPE : MCQ Basic Level (Q.1-Q.15)

1. What is the primary function of a transducer in a process control system?

A) To amplify the process variable
B) To convert one form of energy into another
C) To control the actuator
D) To store process data
Answer: B

2. Which sensor is most suitable for measuring temperature in a high-temperature furnace?

A) Thermistor
B) Thermocouple
C) Resistance Temperature Detector (RTD)
D) Capacitive sensor
Answer: B

3. What does a strain gauge primarily measure?

A) Temperature
B) Pressure
C) Force or deformation
D) Flow rate
Answer: C

4. Which of the following is NOT a characteristic of a good sensor?

A) High sensitivity
B) Fast response time
C) Low accuracy
D) Good linearity
Answer: C

5. In a P&ID diagram, what does the symbol for a valve with a diamond shape represent?

A) Gate valve
B) Control valve
C) Check valve
D) Ball valve
Answer: B

6. What does the abbreviation "FI" stand for in a P&ID diagram?

A) Flow Indicator
B) Flow Integrator
C) Frequency Indicator
D) Force Indicator
Answer: A

7. Which symbol is used to represent a pump in a P&ID diagram?

A) Circle with a triangle inside
B) Diamond with a line through it
C) Square with a cross
D) Circle with a line across
Answer: A

8. What is the purpose of linearization in process modeling?

A) To simplify nonlinear models for analysis
B) To increase the complexity of the model
C) To eliminate process variables
D) To reduce controller tuning
Answer: A

9. A first-order process model is characterized by which of the following?

A) One time constant and no dead time
B) Two time constants and dead time
C) No time constant and dead time
D) Multiple time constants and no dead time
Answer: A

10. What is the transfer function of a pure dead-time process?

A) e^−sTd
B) 1/s
C) 1/(τs+1)
D) s
Answer: A

11. The transfer function of a system relates:

A) Input to output in the time domain
B) Input to output in the frequency domain
C) Output to error in the time domain
D) Input to error in the frequency domain
Answer: B

12. What is the steady-state gain of a first-order system with transfer function K/(τs+1) ?

A) τ
B) K
C) 1/τ
D) K/τ
Answer: B

13. A system with inverse response is characterized by:

A) Initial response in the opposite direction of the final steady state
B) No response to input changes
C) Instantaneous steady-state response
D) Oscillatory response only
Answer: A

14. The process reaction curve method is used to determine:

A) Controller tuning parameters
B) Sensor calibration constants
C) Actuator dynamics
D) Steady-state error
Answer: A

15. What is the dead time in a process reaction curve?

A) Time taken to reach steady state
B) Time before the process begins to respond
C) Time constant of the process
D) Time to reach 63.2% of the final value
Answer: B

TYPE : MCQ Intermediate Level (Q.16-Q.25)

16. Which controller mode eliminates steady-state offset in a control system?

A) Proportional (P)
B) Integral (I)
C) Derivative (D)
D) Proportional-Derivative (PD)
Answer: B

17. What is the primary role of the derivative term in a PID controller?

A) To reduce steady-state error
B) To anticipate rapid changes in error
C) To amplify the control signal
D) To eliminate process noise
Answer: B

18. A proportional-only controller is likely to result in:

A) No steady-state error
B) Oscillatory response
C) Steady-state offset
D) Unstable system
Answer: C

19. What is the function of a control valve in a process control system?

A) To measure the process variable
B) To actuate the final control element
C) To amplify the controller signal
D) To filter process noise
Answer: B

20. Which characteristic of a control valve is preferred for fast-responding processes?

A) Equal percentage
B) Linear
C) Quick-opening
D) Slow-opening
Answer: C

21. The dynamics of a transducer can often be modeled as:

A) A first-order system
B) A second-order system
C) A zero-order system
D) A nonlinear system
Answer: A

22. What affects the response time of a transducer?

A) Process pressure only
B) Time constant of the transducer
C) Controller gain
D) Actuator size
Answer: B

23. The stability of a closed-loop system is determined by:

A) The location of poles in the s-plane
B) The gain of the controller only
C) The time constant of the process
D) The dead time of the system
Answer: A

24. In frequency response analysis, the gain margin indicates:

A) The phase shift at crossover frequency
B) The stability margin at the critical frequency
C) The amplitude ratio at zero frequency
D) The time constant of the system
Answer: B

25. Which tuning method uses the ultimate gain and ultimate period of a system?

A) Ziegler-Nichols method
B) Cohen-Coon method
C) Process reaction curve method
D) Lambda tuning method
Answer: A
Instrumentation and Process Control is a critical subject in GATE Chemical Engineering, contributing 8–12 marks annually from 2020 to 2025.
  • GATE 2026 Instrumentation and Process Control-IPC: Basics Fundamentals Practice 02
  • GATE 2026 Instrumentation and Process Control-IPC: Basics Fundamentals Practice 03
  • GATE 2026 Instrumentation and Process Control-IPC: Numerical Based Practice 01
  • GATE 2026 Instrumentation and Process Control-IPC: Numerical Based Practice 02
  • GATE 2026 Instrumentation and Process Control-IPC: Numerical Based Practice 03

TYPE : MCQ Basic Level (Q.1-Q.15)

1. Which of the following is a fixed cost in a chemical plant?

A) Raw material cost
B) Utility cost
C) Plant overhead cost
D) Maintenance cost
Answer: C
Explanation: Fixed costs are expenses that do not vary with production levels, such as plant overheads (e.g., salaries, taxes). Raw materials, utilities, and maintenance are variable costs.

2. The Chemical Engineering Plant Cost Index (CEPCI) in 2020 was 600, and in 2025, it is 720. If a plant cost $1,000,000 in 2020, what is its estimated cost in 2025?

A) $1,200,000
B) $1,000,000
C) $833,333
D) $1,440,000
Answer: A
Explanation: Cost in 2025 = Cost in 2020 × (CEPCI 2025 / CEPCI 2020) = 1,000,000 × (720 / 600) = $1,200,000.

3. The straight-line depreciation method assumes:

A) Equal depreciation amount each year
B) Decreasing depreciation amount over time
C) Increasing depreciation amount over time
D) No depreciation in the first year
Answer: A
Explanation: Straight-line depreciation allocates the cost of an asset equally over its useful life.

4. A machine costs $100,000 with a salvage value of $10,000 and a useful life of 10 years. Using straight-line depreciation, what is the annual depreciation expense?

A) $10,000
B) $9,000
C) $8,000
D) $12,000
Answer: B
Explanation: Annual depreciation = (Initial cost – Salvage value) / Useful life = (100,000 – 10,000) / 10 = $9,000.

5. A plant has a capital cost of $500,000, annualized over 5 years at 10% interest, and annual operating costs of $50,000. Using the capital recovery factor, what is the total annualized cost? (Capital recovery factor for 5 years at 10% is 0.2638)

A) $181,900
B) $131,900
C) $150,000
D) $200,000
Answer: A
Explanation: Annualized capital cost = 500,000 × 0.2638 = $131,900. Total annualized cost = $131,900 + $50,000 = $181,900.

6. The cost of a heat exchanger in 2023 was $50,000 when the CEPCI was 650. If the CEPCI in 2025 is 715, what is the cost in 2025?

A) $55,000
B) $45,000
C) $60,000
D) $50,000
Answer: A
Explanation: Cost in 2025 = 50,000 × (715 / 650) = $55,000.

7. The internal rate of return (IRR) is the discount rate at which:

A) Net present value (NPV) is zero
B) Payback period is minimized
C) Total annualized cost is maximized
D) Initial investment is doubled
Answer: A
Explanation: IRR is the rate that makes the NPV of cash flows equal to zero.

8. A project requires an initial investment of $200,000 and generates $60,000 annually for 5 years. If the IRR is approximately 10% (NPV ≈ 0), what is the NPV at a discount rate of 8%? (Present value factor for 5 years at 8% is 3.9927)

A) $39,562
B) $0
C) -$39,562
D) $60,000
Answer: A
Explanation: NPV = (60,000 × 3.9927) – 200,000 = $239,562 – $200,000 = $39,562.

9. The payback period is defined as:

A) Time to recover initial investment from cumulative cash flows
B) Time to double the initial investment
C) Time until NPV becomes zero
D) Time until IRR exceeds 10%
Answer: A
Explanation: Payback period is the time required to recover the initial investment through cash inflows.

10. A project costs $300,000 and generates $100,000 per year. What is the payback period?

A) 2 years
B) 3 years
C) 4 years
D) 5 years
Answer: B
Explanation: Payback period = $300,000 / $100,000 = 3 years.

11. The profitability index (PI) is defined as:

A) Total cost / NPV
B) Present value of cash inflows / Initial investment
C) IRR / Discount rate
D) Annual cash flow / Payback period
Answer: B
Explanation: Profitability Index = Present value of future cash inflows divided by the initial investment. It helps in ranking investment projects.

12. A project has a PI of 1.2. What does this indicate?

A) Project is not viable
B) Project returns are 120% of cost
C) IRR is less than 0
D) Payback period is 1.2 years
Answer: B
Explanation: A PI of 1.2 means the project will return $1.20 for every $1 invested, indicating a profitable investment.

13. Which method does NOT consider the time value of money?

A) NPV
B) IRR
C) Payback Period
D) Discounted Payback Period
Answer: C
Explanation: The regular payback period method ignores the time value of money and only considers cumulative cash flows.

14. In capital budgeting, sunk cost is:

A) A recoverable cost
B) A future cost
C) An irrelevant cost
D) A variable cost
Answer: C
Explanation: Sunk costs are past costs that cannot be recovered and should not influence future investment decisions.

15. Break-even point occurs when:

A) Revenue = Variable cost
B) Revenue = Fixed cost
C) Revenue = Total cost
D) Revenue = Profit
Answer: C
Explanation: Break-even occurs when total revenue equals total costs (fixed + variable), resulting in zero profit or loss.

Estimated Weightage for Plant Design and Economics: 4–6 marks (5–8% of total marks)

Typically, 2–3 questions are expected:

1–2 questions (1 mark each): Conceptual questions on topics like cost estimation, depreciation, or payback period.

1 question (2 marks): Calculation-based question involving total annualized cost, discounted cash flow, or equipment sizing (e.g., heat exchangers).

  • GATE 2026 Plant Design and Economics-PDE: Basics Fundamentals Practice 02
  • GATE 2026 Plant Design and Economics-PDE: Basics Fundamentals Practice 03
  • GATE 2026 Plant Design and Economics-PDE: Numerical Based Practice 01
  • GATE 2026 Plant Design and Economics-PDE: Numerical Based Practice 02
  • GATE 2026 Plant Design and Economics-PDE: Numerical Based Practice 03

TYPE : MCQ Basic Level (Q.1-Q.20)

1. Sulfuric Acid Production: In the contact process for sulfuric acid production, the catalyst used is:

A) Platinum
B) Vanadium pentoxide (V₂O₅)
C) Iron oxide
D) Nickel
Answer: B

2. Sulfuric Acid Process: The primary purpose of the absorption tower in the contact process is to:

A) Convert SO₂ to SO₃
B) Absorb SO₃ into water to form H₂SO₄
C) Remove impurities from sulfur
D) Cool the reaction gases
Answer: B

3. Phosphoric Acid Production: The wet process for phosphoric acid production involves the reaction of phosphate rock with:

A) Nitric acid
B) Sulfuric acid
C) Hydrochloric acid
D) Phosphoric acid
Answer: B

4. Chlor-Alkali Industry: In the chlor-alkali process, which product is formed at the cathode in the diaphragm cell?

A) Chlorine gas
B) Sodium hydroxide
C) Hydrogen gas
D) Sodium chloride
Answer: C

5. Chlor-Alkali Industry: The membrane cell process in the chlor-alkali industry uses a membrane made of:

A) Asbestos
B) Teflon-based polymer
C) Graphite
D) Stainless steel
Answer: B

6. Ammonia Production: The Haber-Bosch process for ammonia synthesis operates at:

A) Low pressure and high temperature
B) High pressure and moderate temperature
C) Low pressure and low temperature
D) High pressure and high temperature
Answer: B

7. Ammonia Synthesis: The catalyst used in the Haber-Bosch process is:

A) Platinum
B) Iron with promoters
C) Nickel
D) Copper
Answer: B

8. Urea Production: Urea is synthesized by reacting ammonia with:

A) Carbon monoxide
B) Carbon dioxide
C) Nitrogen
D) Sulfur dioxide
Answer: B

9. Single Superphosphate (SSP): The main phosphate compound in single superphosphate (SSP) is:

A) Calcium dihydrogen phosphate
B) Calcium phosphate
C) Ammonium phosphate
D) Triple superphosphate
Answer: A

10. Triple Superphosphate (TSP): Triple superphosphate is produced by reacting phosphate rock with:

A) Sulfuric acid
B) Phosphoric acid
C) Nitric acid
D) Hydrochloric acid
Answer: B

11. Pulp and Paper Industry: The Kraft process in pulp production primarily uses which chemical to digest wood chips?

A) Sodium hydroxide and sodium sulfide
B) Sulfuric acid
C) Calcium carbonate
D) Chlorine
Answer: A

12. Pulp and Paper Industry: The primary purpose of bleaching in the paper industry is to:

A) Increase the strength of paper
B) Remove lignin and improve whiteness
C) Reduce water content
D) Enhance fiber bonding
Answer: B

13. Sugar Industry: In sugar production, the clarification of cane juice involves the addition of:

A) Sodium hydroxide
B) Lime (calcium hydroxide)
C) Sulfuric acid
D) Ammonia
Answer: B

14. Oil and Fats Industry: The process of hydrogenation in the oil and fats industry is used to:

A) Remove impurities
B) Convert liquid oils to solid fats
C) Extract oil from seeds
D) Increase the shelf life of oils
Answer: B

15. Oil and Fats Industry: The main raw material for soap production in the oil and fats industry is:

A) Glycerol
B) Fatty acids
C) Paraffins
D) Esters
Answer: B

16. In the Contact Process for sulfuric acid manufacture, vanadium pentoxide is used as a catalyst primarily because:

A) It minimizes SO₂ emissions
B) It withstands high temperature and has high selectivity
C) It oxidizes SO₃ to SO₂ effectively
D) It acts as a dehydrating agent
Answer: B

17. The critical challenge in the production of phosphoric acid via the wet process is:

A) Handling of toxic by-products like HF
B) Recovery of ammonia
C) Large energy requirement
D) High-pressure reactor handling
Answer: A

18. In the chlor-alkali industry, membrane cell technology is preferred over diaphragm and mercury cells due to:

A) Higher current efficiency
B) Zero environmental impact
C) High operating pressure compatibility
D) Use of asbestos in membrane
Answer: A

19. In the production of urea from ammonia and CO₂, the unconverted materials are recycled due to:

A) Reaction irreversibility
B) High equilibrium conversion and low cost
C) High temperature sensitivity of the process
D) Economic limitations of one-pass conversion
Answer: D

20. Which of the following best explains the function of formaldehyde in the production of urea-formaldehyde resin?

A) Acts as a chain initiator
B) Provides nitrogen
C) Functions as a cross-linking agent
D) Inhibits polymerization
Answer: C

TYPE : MCQ Intermediate Level (Q.21-Q.25)

21. In pulp and paper industry, the Kraft process is advantageous over sulfite process due to:

A) Lower capital cost
B) Superior bleaching requirements
C) Recovery and reuse of chemicals
D) Use of organic solvents
Answer: C
Explanation: The Kraft process recovers chemicals like NaOH and Na₂S through the recovery boiler system.

22. The saponification number of oil or fat provides an estimate of:

A) The amount of unsaturation
B) Average molecular weight of fatty acids
C) Presence of triglycerides
D) Thermal degradation level
Answer: B
Explanation: Saponification number inversely indicates average molecular weight of the fatty acids.

23. In the steam cracking process for ethylene production, the severity of cracking is primarily controlled by:

A) Addition of hydrogen
B) Hydrocarbon feed composition
C) Cracking furnace residence time and temperature
D) Recycle gas composition
Answer: C
Explanation: Severity depends on how long and at what temperature the hydrocarbons are exposed in the furnace.

24. During the polymerization of vinyl chloride to form PVC, the addition of plasticizers results in:

A) Increased crystallinity
B) Higher glass transition temperature
C) Improved flexibility and processability
D) Faster polymerization
Answer: C
Explanation: Plasticizers reduce intermolecular forces, making the polymer more flexible and easier to process.

25. The main monomers involved in the production of polyester synthetic fibers are:

A) Terephthalic acid and ethylene glycol
B) Propylene and sulfur dioxide
C) Vinyl chloride and acetic acid
D) Styrene and butadiene
Answer: A
Explanation: Polyester fibers like PET are formed by condensation polymerization of terephthalic acid and ethylene glycol.
  • GATE 2026 Chemical Technology-CT: Basics Fundamentals Practice 01
  • GATE 2026 Chemical Technology-CT: Basics Fundamentals Practice 02
  • GATE 2026 Chemical Technology-CT: Basics Fundamentals Practice 03
  • GATE 2026 Chemical Technology-CT: Numerical Based Practice 01
  • GATE 2026 Chemical Technology-CT: Numerical Based Practice 02
  • GATE 2026 Chemical Technology-CT: Numerical Based Practice 03

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